The invention addresses a polymer coated paperboard which is an improvement over current structures and can be utilized for dual ovenable applications. The polymer coating contains a product contact layer of a polyethylene terephthalate polyester. The structure makes use of an unique adhesive tie material selected from the group including ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-ethyl acrylate-maleic anhydride terpolymer, and ethylene-butyl acrylate-maleic anhydride terpolymer. The unique adhesive tie material may be combined with an antioxidant and/or inorganic fillers.
In the past, dual ovenable containers have been constructed from a laminate containing paperboard, a tie layer of ethylene-methyl acrylate (EMA), ethylene-vinyl acetate copolymers, acrylic acid copolymers, physical blends of polyethylene with about 20% polyethylene terephthalate (PET) or physical blends of ethylene-methyl acrylate with polyethylene terephthalate. See U.S. Pat. No. 4,455,184.
The unique tie materials for polyethylene terephthalate of the present invention are neither discussed nor suggested by the '184 patent. These tie materials can withstand high temperature conditions and remain stable. This allows the container produced to exhibit the necessary and superior cooking performance. The superior adhesive tie materials and resultant structures allow for coating weights of the polyester to be below 25 lbs/3,000 sq. ft., something not previously successfully practical with prior polyethylene terephthalate structures. In the past, weights below 25 lbs/3,000 sq. ft. of polyethylene terephthalate exhibited poor adhesion to the paperboard substrate, in addition to deleterious pinholes formed therein. Reduction of the coating weights of the product contact layer provided significant economic savings in production of the structure, and can be accomplished through the use of the unique adhesive tie materials which incorporate an antioxidant.
It is an object of the present invention to produce a coating for contact with a product in a dual ovenable container that is less costly than conventional structures and maintains product quality.
It is a further object of the present invention to reduce coating neck-in and therefor reduce paperboard trimming requirements and thus reduce paperboard waste.
It is yet a further object of the present invention to increase adhesion of the product contact layer coating to paperboard.
Another object of the present invention is to increase flexibility of the coating structure.
Another object of the present invention is to increase coating line speed without causing detrimental effect on the quality of products being produced.
Yet another object of the present invention is the production of high temperature cooking coated paper containers.